Scale Invariance of Immune System Response Rates and Times: Perspectives on Immune System Architecture and Implications for Artificial Immune Systems

TL;DR

This paper demonstrates that the natural immune system maintains scale-invariant response rates across different organism sizes due to a sub-modular architecture, informing the design of efficient artificial immune systems and distributed networks.

Contribution

It reveals the scale-invariant nature of immune responses and proposes a sub-modular architecture as an efficient design principle for both biological and artificial immune systems.

Findings

Immune response rates do not systematically vary with body size.

A sub-modular architecture balances local detection and global response efficiently.

Artificial immune systems benefit from sub-modular designs for distributed problem-solving.

Abstract

Most biological rates and times decrease systematically with organism body size. We use an ordinary differential equation (ODE) model of West Nile Virus in birds to show that pathogen replication rates decline with host body size, but natural immune system (NIS) response rates do not change systematically with body size. This is surprising since the NIS has to search for small quantities of pathogens through larger physical spaces in larger organisms, and also respond by producing larger absolute quantities of antibody in larger organisms. We call this scale-invariant detection and response. We hypothesize that the NIS has evolved an architecture to efficiently neutralize pathogens. We investigate a range of architectures using an Agent Based Model (ABM). We find that a sub-modular NIS architecture, in which lymph node number and size both increase sublinearly with body size, efficiently balances the tradeoff between local pathogen detection and global response using antibodies. This leads to nearly scale-invariant detection and response, consistent with experimental data. Similar to the NIS, physical space and resources are also important constraints on Artificial Immune Systems (AIS), especially distributed systems applications used to connect low-powered sensors using short-range wireless communication. We show that AIS problems, like distributed robot control, will also require a sub-modular architecture to efficiently balance the tradeoff between local search for a solution and global response or proliferation of the solution between different components. This research has wide applicability in other distributed systems AIS applications.